Chemical mechanical polishing method for tungsten

ABSTRACT

A process for chemical mechanical polishing a substrate containing tungsten is disclosed to reduce static corrosion rate and inhibit dishing of the tungsten and erosion of underlying dielectrics. The process includes providing a substrate; providing a polishing composition, containing, as initial components: water; an oxidizing agent; guar gum; a dicarboxylic acid, a source of iron ions; a colloidal silica abrasive; and, optionally a pH adjusting agent; providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the polishing pad and the substrate; and dispensing the polishing composition onto the polishing surface at or near the interface between the polishing pad and the substrate; wherein some of the tungsten (W) is polished away from the substrate, static corrosion rate is reduced, dishing of the tungsten (W) is inhibited as well as erosion of dielectrics underlying the tungsten (W).

FIELD OF THE INVENTION

The present invention is directed to the field of chemical mechanicalpolishing of tungsten to inhibit dishing of the tungsten in combinationwith inhibiting erosion of underlying dielectrics and to reduce staticcorrosion rate. More specifically, the present invention is directed toa method for chemical mechanical polishing of tungsten to inhibitdishing of the tungsten in combination with inhibiting erosion ofunderlying dielectrics and to reduce corrosion rate by providing asubstrate containing tungsten; providing a polishing composition,containing, as initial components: water; an oxidizing agent; guar gum;a dicarboxylic acid, a source of iron ions; a colloidal silica abrasive;and, optionally a pH adjusting agent; providing a chemical mechanicalpolishing pad, having a polishing surface; creating dynamic contact atan interface between the polishing pad and the substrate; and dispensingthe polishing composition onto the polishing surface at or near theinterface between the polishing pad and the substrate where some of thetungsten is polished away from the substrate.

BACKGROUND OF THE INVENTION

In the fabrication of integrated circuits and other electronic devices,multiple layers of conducting, semiconducting and dielectric materialsare deposited on or removed from a surface of a semiconductor wafer.Thin layers of conducting, semiconducting, and dielectric materials maybe deposited by a number of deposition techniques. Common depositiontechniques in modern processing include physical vapor deposition (PVD),also known as sputtering, chemical vapor deposition (CVD),plasma-enhanced chemical vapor deposition (PECVD), and electrochemicalplating (ECP).

As layers of materials are sequentially deposited and removed, theuppermost surface of the wafer becomes non-planar. Because subsequentsemiconductor processing (e.g., metallization) requires the wafer tohave a flat surface, the wafer needs to be planarized. Planarization isuseful in removing undesired surface topography and surface defects,such as rough surfaces, agglomerated materials, crystal lattice damage,scratches, and contaminated layers or materials.

Chemical mechanical planarization, or chemical mechanical polishing(CMP), is a common technique used to planarize substrates, such assemiconductor wafers. In conventional CMP, a wafer is mounted on acarrier assembly and positioned in contact with a polishing pad in a CMPapparatus. The carrier assembly provides a controllable pressure to thewafer, pressing it against the polishing pad. The pad is moved (e.g.,rotated) relative to the wafer by an external driving force.Simultaneously therewith, a polishing composition (“slurry”) or otherpolishing solution is provided between the wafer and the polishing pad.Thus, the wafer surface is polished and made planar by the chemical andmechanical action of the pad surface and slurry.

Substrates in the electronics industry possess a high degree ofintegration where semiconductor bases include multilayers ofinterconnected structures. The layers and the structures include a widevariety of materials such as single crystal silicon, polycrystallinesilicon, tetraethyl orthosilicate, silicon dioxide, silicon nitride,tungsten, titanium, titanium nitride and various other conductive,semiconductive and dielectric materials. Because these substratesrequire various processing steps, including CMP to form a finalmultilayered interconnected structure, it is often highly desirable toutilize polishing compositions and processes that are selective forspecific materials depending on the intended applications.Unfortunately, such polishing compositions can cause excessive dishingof the conductive material which can lead to erosion of dielectricmaterial. The topographical defects which can result from such dishingand erosion can further lead to non-uniform removal of additionalmaterials from the substrate surface, such as barrier layer materialdisposed beneath the conductive material or dielectric material andproduce a substrate surface having less than desirable quality which cannegatively impact the performance of the integrated circuit.

Chemical mechanical polishing has become a preferred method forpolishing tungsten during the formation of tungsten interconnects andcontact plugs in integrated circuit designs. Tungsten is frequently usedin integrated circuit designs for contact/via plugs. Typically, acontact or via hole is formed through a dielectric layer on a substrateto expose regions of an underlying component, for example, a first levelmetallization or interconnect. Unfortunately, many CMP slurries used topolish tungsten cause the problem of dishing. The severity of thedishing can vary but it typically is severe enough to cause erosion ofunderlying dielectric materials such as TEOS.

Another problem associated with polishing metals such as tungsten iscorrosion. The corrosion of metals is a common side-effect of CMP.During the CMP process the metal polishing slurry that remains on thesurface of the substrate continues to corrode the substrate beyond theeffects of the CMP. Sometimes corrosion is desired; however, in mostsemiconductor processes corrosion is to be reduced or inhibited.Corrosion may also contribute to surface defects such as pitting andkey-holing. These surface defects significantly affect the finalproperties of the semiconductor device and hamper its usefulness.Therefore, there is a need for a CMP polishing method and compositionfor tungsten which inhibits dishing of tungsten and erosion ofunderlying dielectric materials such as TEOS and also reduces staticcorrosion rate.

SUMMARY OF THE INVENTION

The present invention provides a method of chemical mechanical polishingtungsten, comprising: providing a substrate comprising tungsten and adielectric; providing a chemical mechanical polishing composition,comprising, as initial components: water; an oxidizing agent; guar gum;a colloidal silica abrasive; a dicarboxylic acid or salt thereof; asource of iron (III) ions; and, optionally, a pH adjusting agent;providing a chemical mechanical polishing pad, having a polishingsurface; creating dynamic contact at an interface between the chemicalmechanical polishing pad and the substrate; and dispensing the chemicalmechanical polishing composition onto the polishing surface of thechemical mechanical polishing pad at or near the interface between thechemical mechanical polishing pad and the substrate; wherein some of thetungsten is polished away from the substrate.

The present invention provides a chemical mechanical method of polishingtungsten, comprising: providing the substrate comprising tungsten and adielectric; providing a chemical mechanical polishing composition,comprising, as initial components: water; an oxidizing agent; guar gum;a colloidal silica abrasive having a negative zeta potential; adicarboxylic acid or salt thereof; a source of iron (III) ions; and,optionally, a pH adjusting agent; providing a chemical mechanicalpolishing pad, having a polishing surface; creating dynamic contact atan interface between the chemical mechanical polishing pad and thesubstrate; and dispensing the chemical mechanical polishing compositiononto the polishing surface of the chemical mechanical polishing pad ator near the interface between the chemical mechanical polishing pad andthe substrate; wherein some of the tungsten is polished away from thesubstrate; wherein the chemical mechanical polishing compositionprovided has a tungsten removal rate of ≥1,000 Å/min with a platen speedof 80 revolutions per minute, a carrier speed of 81 revolutions perminute, a chemical mechanical polishing composition flow rate of 125mL/min, a nominal down force of 21.4 kPa on a 200 mm polishing machine;and, wherein the chemical mechanical polishing pad comprises apolyurethane polishing layer containing polymeric hollow coremicroparticles and a polyurethane impregnated non-woven subpad.

The present invention provides a chemical mechanical method of polishingtungsten, comprising: providing a substrate comprising tungsten and adielectric; providing a chemical mechanical polishing composition,comprising, as initial components: water; an oxidizing agent; guar gumin an amount of at least 50 ppm; a colloidal silica abrasive having anegative zeta potential; malonic acid or salt thereof; a source of iron(III) ions; and, optionally, a pH adjusting agent; providing a chemicalmechanical polishing pad, having a polishing surface; creating dynamiccontact at an interface between the chemical mechanical polishing padand the substrate; and dispensing the chemical mechanical polishingcomposition onto the polishing surface of the chemical mechanicalpolishing pad at or near the interface between the chemical mechanicalpolishing pad and the substrate; wherein some of the tungsten ispolished away from the substrate; wherein the chemical mechanicalpolishing composition provided has a tungsten removal rate of ≥1,000Å/min with a platen speed of 80 revolutions per minute, a carrier speedof 81 revolutions per minute, a chemical mechanical polishingcomposition flow rate of 125 mL/min, a nominal down force of 21.4 kPa ona 200 mm polishing machine; wherein the chemical mechanical polishingpad comprises a polyurethane polishing layer containing polymeric hollowcore microparticles and a polyurethane impregnated non-woven subpad.

The present invention provides a method of chemical mechanical polishingtungsten, comprising: providing the substrate comprising tungsten and adielectric; providing a chemical mechanical polishing composition,comprising, as initial components: water; 0.01 to 10 wt % of anoxidizing agent, wherein the oxidizing agent is hydrogen peroxide; 50ppm to 1000 ppm of guar gum; 0.01 to 10 wt % of a colloidal silicaabrasive having a negative zeta potential; 100 to 1,400 ppm malonic acidor salt thereof; 100 to 1,000 ppm of a source of iron (III) ions,wherein the source of iron (III) ions is ferric nitrate nonahydrate;and, optionally, a pH adjusting agent; wherein the chemical mechanicalpolishing composition has a pH of 1 to 7; providing a chemicalmechanical polishing pad, having a polishing surface; creating dynamiccontact at an interface between the chemical mechanical polishing padand the substrate; and dispensing the chemical mechanical polishingcomposition onto the polishing surface of the chemical mechanicalpolishing pad at or near the interface between the chemical mechanicalpolishing pad and the substrate; wherein some of the tungsten ispolished away from the substrate.

The present invention provides a method of chemical mechanical polishingtungsten, comprising: providing a substrate comprising tungsten and adielectric; providing a chemical mechanical polishing composition,comprising, as initial components: water; 1 to 3 wt % of an oxidizingagent, wherein the oxidizing agent is hydrogen peroxide; 50 to 500 ppmguar gum, 0.2 to 2 wt % of a colloidal silica abrasive having a negativesurface charge; 120 to 1,350 ppm of malonic acid; 250 to 400 ppm of asource of iron (III) ions, wherein the source of iron (III) ions isferric nitrate nonahydrate; and, optionally, a pH adjusting agent;wherein the chemical mechanical polishing composition has a pH of 2 to2.5; providing a chemical mechanical polishing pad, having a polishingsurface; creating dynamic contact at an interface between the chemicalmechanical polishing pad and the substrate; and dispensing the chemicalmechanical polishing composition onto the polishing surface of thechemical mechanical polishing pad at or near the interface between thechemical mechanical polishing pad and the substrate; wherein some of thetungsten is polished away from the substrate.

The foregoing methods of the present invention use a chemical mechanicalpolishing composition comprising guar gum which polishes tungsten andinhibits dishing of the tungsten in combination with inhibiting erosionof underlying dielectrics. The method also reduces static corrosionrate.

DETAILED DESCRIPTION OF THE INVENTION

As used throughout this specification the following abbreviations havethe following meanings, unless the context indicates otherwise: °C.=degrees Centigrade; g=grams; L=liters; mL=milliliters; μ=μm=microns;kPa=kilopascal; Å=angstroms; mV=millivolts; DI=deionized; ppm=parts permillion=mg/L; mm=millimeters; cm=centimeter; min=minute; rpm=revolutionsper minute; lbs=pounds; kg=kilograms; W=tungsten; PO=propylene oxide;EO=ethylene oxide; ICP-OES=inductively coupled plasma optical emissionspectroscopy; wt %=percent by weight; and RR=removal rate.

The term “chemical mechanical polishing” or “CMP” refers to a processwhere a substrate is polished by means of chemical and mechanical forcesalone and is distinguished from electrochemical-mechanical polishing(ECMP) where an electric bias is applied to the substrate. The term“guar gum” means a polysaccharide composed of the sugars galactose andmannose wherein the backbone is a linear chain of β 1,4-linked mannoseresidues to which galactose residues are 1,6-linked at every secondmannose, forming short side-branches. The term “starch” means apolysaccharide composed of a large number of glucose units joined byglycosidic bonds. The term “TEOS” means the silicon dioxide formed fromtetraethyl orthosilicate (Si(OC₂H₅)₄). The terms “a” and “an” refer toboth the singular and the plural. All percentages are by weight, unlessotherwise noted. All numerical ranges are inclusive and combinable inany order, except where it is logical that such numerical ranges areconstrained to add up to 100%.

The method of polishing a substrate of the present invention uses achemical mechanical polishing composition containing an oxidizing agent;guar gum; a colloidal silica abrasive; a dicarboxylic acid or saltthereof; a source of iron (III) ions; and, optionally, a pH adjustingagent to provide for the removal of tungsten from the substrate surfacewhile inhibiting dishing of the tungsten, erosion of underlyingdielectric materials and reducing corrosion rate.

Preferably, the method of polishing a substrate of the presentinvention, comprises: providing the substrate, wherein the substratecomprises tungsten and a dielectric; providing a chemical mechanicalpolishing composition, comprising, preferably, consisting of, as initialcomponents: water; an oxidizing agent, preferably in amounts of at least0.01 wt % to 10 wt %, more preferably in amounts of 0.1 wt % to 5 wt %,still more preferably from 1 wt % to 3 wt %; guar gum in amounts of,preferably, at least 50 ppm, more preferably 50 ppm to 1000 ppm, evenmore preferably from 50 ppm to 500 ppm, still more preferably from 100ppm to 250 ppm; a colloidal silica abrasive, preferably in amounts of0.01 wt % to 10 wt %, more preferably from 0.05 wt % to 7.5 wt %, evenmore preferably from 0.1 wt % to 5 wt %, still more preferably from 0.2wt % to 2 wt %; a dicarboxylic acid, salt thereof or mixtures thereof,preferably in amounts of 100 ppm to 1400 ppm, more preferably from 120ppm to 1350 ppm; a source of iron (III) ions, preferably, wherein thesource of iron (III) ions is ferric nitrate nonahydrate; and,optionally, a pH adjusting agent; preferably, wherein the chemicalmechanical polishing composition has a pH of 1 to 7; more preferably, of1.5 to 4.5; still more preferably, 1.5 to 3.5; most preferably, of 2 to2.5; providing a chemical mechanical polishing pad, having a polishingsurface; creating dynamic contact at an interface between the chemicalmechanical polishing pad and the substrate; and dispensing the chemicalmechanical polishing composition onto the polishing surface of thechemical mechanical polishing pad at or near the interface between thechemical mechanical polishing pad and the substrate; wherein at leastsome of the tungsten is polished away from the substrate.

Preferably, in the method of polishing a substrate of the presentinvention, the substrate comprises tungsten and a dielectric. Morepreferably, the substrate provided is a semiconductor substratecomprising tungsten and a dielectric. Most preferably, the substrateprovided is a semiconductor substrate comprising tungsten depositedwithin at least one of holes and trenches formed in a dielectric such asTEOS.

Preferably, in the method of polishing a substrate of the presentinvention, the water contained, as an initial component, in the chemicalmechanical polishing composition provided is at least one of deionizedand distilled to limit incidental impurities.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, an oxidizing agent, wherein theoxidizing agent is selected from the group consisting of hydrogenperoxide (H₂O₂), monopersulfates, iodates, magnesium perphthalate,peracetic acid and other per-acids, persulfate, bromates, perbromate,persulfate, peracetic acid, periodate, nitrates, iron salts, ceriumsalts, Mn (III), Mn (IV) and Mn (VI) salts, silver salts, copper salts,chromium salts, cobalt salts, halogens, hypochlorites and a mixturethereof. More preferably, the oxidizing agent is selected from hydrogenperoxide, perchlorate, perbromate; periodate, persulfate and peraceticacid. Most preferably, the oxidizing agent is hydrogen peroxide.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, 0.01 to 10 wt %, more preferably, 0.1to 5 wt %; most preferably, 1 to 3 wt % of an oxidizing agent.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, a source of iron (III) ions. Morepreferably, in the method of the present invention, the chemicalmechanical polishing composition provided contains, as an initialcomponent, a source of iron (III) ions, wherein the source of iron (III)ions is selected from the group consisting iron (III) salts. Mostpreferably, in the method of the present invention, the chemicalmechanical polishing composition provided contains, as an initialcomponent, a source of iron (III) ions, wherein the source of iron (III)ions is ferric nitrate nonahydrate, (Fe(NO₃)₃.9H₂O).

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, a source of iron (III) ionssufficient to introduce 1 to 200 ppm, preferably, 5 to 150 ppm, morepreferably, 7.5 to 125 ppm, most preferably, 10 to 100 ppm of iron (III)ions to the chemical mechanical polishing composition.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, a source of iron (III) ions. Morepreferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, 100 to 1,000 ppm, preferably, 150 to750 ppm, more preferably, 200 to 500 ppm and most preferably, 250 to 400ppm of a source of iron (III) ions. Most preferably, in the method ofpolishing a substrate of the present invention, the chemical mechanicalpolishing composition provided contains, as an initial component, 100 to1,000 ppm, preferably, 150 to 750 ppm, more preferably, 200 to 500 ppm,most preferably, 250 to 400 ppm of a source of iron (III) ions, whereinthe source of iron (III) ions is ferric nitrate nonahydrate,(Fe(NO₃)₃.9H₂O).

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, guar gum. Preferably, in the methodof polishing a substrate of the present invention, the chemicalmechanical polishing composition provided contains, as an initialcomponent, at least 50 ppm, more preferably 50 ppm to 1000 ppm, evenmore preferably from 50 ppm to 500 ppm, still more preferably from 100ppm to 250 ppm of guar gum. Most preferably in the method of the presentinvention, the chemical mechanical polishing composition providedcontains 100 ppm to 200 ppm of guar gum.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains a colloidal silica abrasive having a negative zeta potential.More preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains a colloidal silica abrasive having a permanent negative zetapotential, wherein the chemical mechanical polishing composition has apH of 1 to 7, preferably, of 1.5 to 4.5; more preferably, of 1.5 to 3.5;still more preferably, of 2 to 2.5. Still more preferably, in the methodof polishing a substrate of the present invention, the chemicalmechanical polishing composition provided contains a colloidal silicaabrasive having a permanent negative zeta potential, wherein thechemical mechanical polishing composition has a pH of 1 to 7,preferably, of 1.5 to 4.5; more preferably, of 1.5 to 3.5; still morepreferably, of 2 to 2.5 as indicated by a zeta potential from −0.1 mV to−20 mV.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, a colloidal silica abrasive, whereinthe colloidal silica abrasive has an average particle size ≤100 nm,preferably, 5 to 100 nm; more preferably, 10 to 60 nm; most preferably,20 to 60 nm as measured by dynamic light scattering techniques.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains 0.01 to 10 wt %, preferably 0.05 to 7.5 wt %, more preferably,0.1 to 5 wt %, most preferably, 0.2 to 2 wt % of a colloidal silicaabrasive. Preferably the colloidal silica abrasive has a negative zetapotential.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, a dicarboxylic acid, wherein thedicarboxylic acid includes, but is not limited to malonic acid, oxalicacid, succinic acid, adipic acid, maleic acid, malic acid, glutaricacid, tartaric acid, salts thereof or mixtures thereof. More preferably,in the method of polishing a substrate of the present invention, thechemical mechanical polishing composition provided contains, as aninitial component, a dicarboxylic acid, wherein the dicarboxylic acid isselected from the group consisting of malonic acid, oxalic acid,succinic acid, tartaric acid, salts thereof and mixtures thereof. Stillmore preferably the chemical mechanical polishing composition providedcontains, as an initial component, a dicarboxylic acid, wherein thedicarboxylic acid is selected from the group consisting of malonic acid,oxalic acid, succinic acid, salts thereof and mixtures thereof. Mostpreferably in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, the dicarboxylic acid malonic acid orsalts thereof.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, 1 to 2,600 ppm, preferably, 100 to1,400 ppm, more preferably, 120 to 1,350 ppm, still more preferably, 130to 1,100 ppm, of a dicarboxylic acid, wherein the dicarboxylic acidincludes, but is not limited to malonic acid, oxalic acid, succinicacid, adipic acid, maleic acid, malic acid, glutaric acid, tartaricacid, salts thereof or mixtures thereof. More preferably, in the methodof polishing a substrate of the present invention, the chemicalmechanical polishing composition provided contains, as an initialcomponent, 1 to 2,600 ppm of malonic acid, salt thereof or mixturesthereof. Most preferably, in the method of polishing a substrate of thepresent invention, the chemical mechanical polishing compositionprovided contains, as an initial component 100 to 1,400 ppm, morepreferably, 120 to 1,350 ppm, still more preferably, 130 to 1,350 ppm,the dicarboxylic acid malonic acid or salts thereof.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition provided has apH of 1 to 7. More preferably, in the method of polishing a substrate ofthe present invention, the chemical mechanical polishing compositionprovided has a pH of 1.5 to 4.5. Still more preferably, in the method ofpolishing a substrate of the present invention, the chemical mechanicalpolishing composition provided has a pH of 1.5 to 3.5. Most preferably,in the method of polishing a substrate of the present invention, thechemical mechanical polishing composition provided has a pH of 2 to 2.5.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedoptionally contains a pH adjusting agent. Preferably, the pH adjustingagent is selected from the group consisting of inorganic and organic pHadjusting agents. Preferably, the pH adjusting agent is selected fromthe group consisting of inorganic acids and inorganic bases. Morepreferably, the pH adjusting agent is selected from the group consistingof nitric acid and potassium hydroxide. Most preferably, the pHadjusting agent is potassium hydroxide.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing pad provided can by anysuitable polishing pad known in the art. One of ordinary skill in theart knows to select an appropriate chemical mechanical polishing pad foruse in the method of the present invention. More preferably, in themethod of polishing a substrate of the present invention, the chemicalmechanical polishing pad provided is selected from woven and non-wovenpolishing pads. Still more preferably, in the method of polishing asubstrate of the present invention, the chemical mechanical polishingpad provided comprises a polyurethane polishing layer. Most preferably,in the method of polishing a substrate of the present invention, thechemical mechanical polishing pad provided comprises a polyurethanepolishing layer containing polymeric hollow core microparticles and apolyurethane impregnated non-woven subpad. Preferably, the chemicalmechanical polishing pad provided has at least one groove on thepolishing surface.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition provided isdispensed onto a polishing surface of the chemical mechanical polishingpad provided at or near an interface between the chemical mechanicalpolishing pad and the substrate.

Preferably, in the method of polishing a substrate of the presentinvention, dynamic contact is created at the interface between thechemical mechanical polishing pad provided and the substrate with a downforce of 0.69 to 34.5 kPa normal to a surface of the substrate beingpolished.

Preferably, in the method of polishing a substrate of the presentinvention, wherein the chemical mechanical polishing compositionprovided has a tungsten removal rate ≥1,000 Å/min; preferably, ≥1,500Å/min; more preferably, ≥2,000 Å/min. More preferably, in the method ofpolishing a substrate of the present invention, wherein the chemicalmechanical polishing composition provided has a tungsten removal rate of≥1,000 Å/min; preferably, ≥1,500 Å/min; more preferably, ≥2,000 Å/min;and a W/TEOS selectivity of ≥5. Still more preferably, in the method ofpolishing a substrate of the present invention, wherein the tungsten isremoved from the substrate at a removal rate of ≥1,000 Å/min;preferably, ≥1,500 Å/min; more preferably, ≥2,000 Å/min; and a W/TEOSselectivity of 5 to 15. Most preferably, in the method of polishing thesubstrate of the present invention, wherein the tungsten is removed fromthe substrate at a removal rate of ≥1,000 Å/min; preferably, ≥1,500Å/min; more preferably, ≥2,000 Å/min; and a W/TEOS selectivity and witha platen speed of 80 revolutions per minute, a carrier speed of 81revolutions per minute, a chemical mechanical polishing composition flowrate of 125 mL/min, a nominal down force of 21.4 kPa on a 200 mmpolishing machine; and, wherein the chemical mechanical polishing padcomprises a polyurethane polishing layer containing polymeric hollowcore microparticles and a polyurethane impregnated non-woven subpad.

As is illustrated in the following Examples, the guar gum CMP methods ofthe present invention inhibit tungsten dishing in combination withinhibiting erosion of underlying TEOS and further inhibits staticcorrosion rate.

Example 1 Slurry Formulations

The chemical mechanical polishing compositions of this Example wereprepared by combining the components in the amounts listed in Table 1with the balance being DI water and adjusting the pH of the compositionsto the final pH listed in Table 1 with 45 wt % potassium hydroxide.

TABLE 1 Malonic Abrasive¹ Polysaccharide Fe(NO₃)₃ Acid H₂O₂ Slurry # (wt%) (ppm) (ppm) (ppm) (wt %) pH CS-1 2 — 362 1320 2 2.3 PS-1 2 Starch(150) 362 1320 2 2.3 PS-2 2 Guar Gum 362 1320 2 2.3 (150) ¹KLEBOSOL ™1598-B25 (—) zeta potential abrasive slurry manufactured by AZElectronics Materials, available from The Dow Chemical Company; and

Example 2 Static Corrosion Rate Performance of Polysaccharide CMPSlurries

The static corrosion tests were carried out by immersing W blanketwafers (1 cm×4 cm) in 15 g slurry samples. The W wafers were removedfrom tested slurries after 10 min. The solutions were subsequentlycentrifuged for 20 min at 9,000 rpm to remove slurry particles. Thesupernatant was analyzed by ICP-OES to determine the amount of tungstenby weight. The static corrosion rate (Å/min) was converted from the Wmass assuming an etching wafer surface area of 4 cm². The results of thestatic corrosion tests are in Table 2.

TABLE 2 Slurry # W Static Corrosion Rate (Å/min) CS-1 29 PS-1 25 PS-2 23

The results of the static corrosion rate tests showed that the chemicalmechanical polishing slurries containing guar gum effectively reducedthe static corrosion on W containing wafers better than the controlslurry (CS-1) as well as to the slurry (PS-1) which included thepolysaccharide starch.

Example 3 Chemical Mechanical Polishing—Dishing and Erosion Performanceof Gur Gum CMP Slurry

The polishing experiments were performed on 200 mm blanket wafersinstalled on an Applied Materials 200 mm MIRRA® polishing machine. Thepolishing removal rate experiments were performed on 200 mm blanket 15kA-thick TEOS sheet wafers plus W, Ti, and TiN blanket wafers availablefrom Silicon Valley Microelectronics. All polishing experiments wereperformed using an IC1010™ polyurethane polishing pad paired with anSP2310 subpad (commercially available from Rohm and Haas ElectronicMaterials CMP Inc.) with a typical down pressure of 21.4 kPa (3.1 psi),a chemical mechanical polishing composition flow rate of 125 mL/min, atable rotation speed of 80 rpm and a carrier rotation speed of 81 rpmunless specified otherwise. A Kinik PDA33A-3 diamond pad conditioner(commercially available from Kinik Company) was used to dress thepolishing pad. The polishing pad was broken in with the conditionerusing a down force of 9.0 lbs (4.1 kg) for 15 minutes and 7.0 lbs (3.2kg) for 15 minutes at 80 rpm (platen)/36 rpm (conditioner). Thepolishing pad was further conditioned ex-situ prior to polishing using adown force of 7 lbs (3.2 kg) for 24 seconds. The TEOS erosion depthswere determined by measuring the film thickness before and afterpolishing using a KLA-Tencor FX200 metrology tool. The W removal anddishing rates were determined using a KLA-Tencor RS100C metrology tool.The wafers had varying standard line width features as shown in Tables3A and 3B. In the tables of this example the numerator refers to W andthe denominator refers to TEOS.

3A 100/100 μm 100/100 μm 50/50 μm 50/50 μm dishing erosion 10/10 μm10/10 μm Slurry # dishing (Å) erosion (Å) (Å) (Å) dishing (Å) erosion(Å) PS-1 1180 57 1337 17 604 236 PS-2 1049 44 1160 21 579 151

3B 0.25/0.25 μm 0.25/0.25 μm 7/3 μm 7/3 μm 9/1 μm 9/1 μm dishing erosionSlurry # dishing (Å) erosion (Å) dishing (Å) erosion (Å) (Å) (Å) PS-1383 610 336 1103 132 336 PS-2 368 523 286 906 154 179

Overall the slurry which included guar gum showed improved performanceover the slurry which included starch. The guar gum slurry showedoverall reduced dishing of W and reduced erosion of TEOS.

Example 4 W, TEOS Removal Rate and W, TEOS Maximum Polishing Temperature

The polishing experiments for W and TEOS removal rates were performedsubstantially as described in Example 3 using the same apparatus andparameters. The wafers were from Silicon Valley Microelectronics. Theresults are in Table 4.

TABLE 4 W RR TEOS RR W/TEOS W Temp. TEOS Temp. Slurry # (Å/min) (Å/min)Selectivity (° C.) (° C.) PS-1 1881 180 10 35 33.7 PS-2 2309 219 11 36.227.6

The guar gum chemical mechanical polishing composition of the presentinvention showed good W RR of greater than 2000 Å/min and good W/TEOSselectivity.

What is claimed is:
 1. A method of chemical mechanical polishingtungsten, comprising: providing a substrate comprising tungsten and adielectric; providing a chemical mechanical polishing composition,comprising, as initial components: water; an oxidizing agent; guar gum;a colloidal silica abrasive; a dicarboxylic acid, a source of iron (III)ions; and, optionally, a pH adjusting agent; providing a chemicalmechanical polishing pad, having a polishing surface; creating dynamiccontact at an interface between the chemical mechanical polishing padand the substrate; and dispensing the chemical mechanical polishingcomposition onto the polishing surface of the chemical mechanicalpolishing pad at or near the interface between the chemical mechanicalpolishing pad and the substrate to remove at least some of the tungsten.2. The method of claim 1, wherein the chemical mechanical polishingcomposition provided has a tungsten removal rate of ≥1,000 Å/min with aplaten speed of 80 revolutions per minute, a carrier speed of 81revolutions per minute, a chemical mechanical polishing composition flowrate of 125 mL/min, a nominal down force of 21.4 kPa on a 200 mmpolishing machine; and, wherein the chemical mechanical polishing padcomprises a polyurethane polishing layer containing polymeric hollowcore microparticles and a polyurethane impregnated non-woven subpad. 3.The method of claim 1, wherein the chemical mechanical polishingcomposition, provided comprises, as initial components: the water; 0.01to 10 wt % of the oxidizing agent, wherein the oxidizing agent ishydrogen peroxide; 50 to 1000 ppm of the guar gum; 0.01 to 10 wt % ofthe colloidal silica abrasive; 1 to 2,600 ppm of the dicarboxylic acid;100 to 1,000 ppm of the source of iron (III) ions, wherein the source ofiron (III) ions is ferric nitrate nonahydrate; and, optionally, the pHadjusting agent; wherein the chemical mechanical polishing compositionhas a pH of 1 to
 7. 4. The method of claim 3, wherein the chemicalmechanical polishing composition provided has a tungsten removal rate of≥1,000 Å/min with a platen speed of 80 revolutions per minute, a carrierspeed of 81 revolutions per minute, a chemical mechanical polishingcomposition flow rate of 125 mL/min, a nominal down force of 21.4 kPa ona 200 mm polishing machine; and, wherein the chemical mechanicalpolishing pad comprises a polyurethane polishing layer containingpolymeric hollow core microparticles and a polyurethane impregnatednon-woven subpad.
 5. The method of claim 1, wherein the chemicalmechanical polishing composition, provided comprises, as initialcomponents: the water; 0.1 to 5 wt % of the oxidizing agent, wherein theoxidizing agent is hydrogen peroxide; 50 to 500 ppm of the guar gum;0.05 to 7.5 wt % of the colloidal silica abrasive; 100 to 1,400 ppm ofthe dicarboxylic acid; 150 to 750 ppm of the source of iron (III) ions,wherein the source of iron (III) ions is ferric nitrate; and,optionally, the pH adjusting agent; wherein the chemical mechanicalpolishing composition has a pH of 1.5 to 4.5.
 6. The method of claim 5,wherein the chemical mechanical polishing composition provided has atungsten removal rate of ≥1,000 Å/min with a platen speed of 80revolutions per minute, a carrier speed of 81 revolutions per minute, achemical mechanical polishing composition flow rate of 125 mL/min, anominal down force of 21.4 kPa on a 200 mm polishing machine; and,wherein the chemical mechanical polishing pad comprises a polyurethanepolishing layer containing polymeric hollow core microparticles and apolyurethane impregnated non-woven subpad.
 7. The method of claim 1,wherein the chemical mechanical polishing composition, providedcomprises, as initial components: the water; 0.1 to 3 wt % of theoxidizing agent, wherein the oxidizing agent is hydrogen peroxide; 100to 250 ppm of the guar gum; 0.1 to 5 wt % of the colloidal silicaabrasive; 120 to 1,350 ppm of the dicarboxylic acid, wherein thedicarboxylic acid is malonic acid; 200 to 500 ppm of the source of iron(III) ions, wherein the source of iron (III) ions is ferric nitrate;and, optionally, the pH adjusting agent; wherein the chemical mechanicalpolishing composition has a pH of 1.5 to 3.5.
 8. The method of claim 7,wherein the chemical mechanical polishing composition provided has atungsten removal rate of ≥1,000 Å/min with a platen speed of 80revolutions per minute, a carrier speed of 81 revolutions per minute, achemical mechanical polishing composition flow rate of 125 mL/min, anominal down force of 21.4 kPa on a 200 mm polishing machine; and,wherein the chemical mechanical polishing pad comprises a polyurethanepolishing layer containing polymeric hollow core microparticles and apolyurethane impregnated non-woven subpad.